Cucurbitane Glycosides from Unripe Fruits of Lo Han Kuo (<i>Siraitia grosvenori</i>)

Abstract

Lo Han Kuo is the fruit of the Siraitia grosvenori SWINGLE (formerly Momordica grosvenori SWINGLE) belonging to Cucurbitaceae species and used as a pulmonary demulcent and emollient for the treatment of dry cough, sore throat, dire thirst, and constipation in traditional Chinese medicine.1) Recently, some intriguing pharmacological characteristics such as anti-cancer and anti-hyperglycemic effects, and inhibition of oxidative modification of low density-lipoprotein were reported.2-4) Therefore it was suggested that a new kind of cancer chemopreventive agent might be developed. A number of cucurbitane triterpene saponins from the ripe fruits were previously obtained. [5][6][7][8][9][10][11][12] Some compounds among them are extremely sweet, such as mogroside V (7) and mogroside IVA (6), and their relative sweetnesses were more than 300 times as high as that of sucrose despite having minimal caloric content. However, it also contains minor tasteless, even bitter principle, such as mogroside III (5) and mogroside IIE (4). The ripe fruit mainly contains mogroside V (7), so it is very sweet. On the basis of these characteristics, its extract is commercially utilized as a sweet component in sugar substitute, that is widely used as additive and ingredient in health foods and beverages. Owing to the influence of cold weather during winter, some fruits cannot mature naturally. The unripe fruits have bitter taste, and at the place of cultivation, these may amount to one quarter of total production. Until now, no chemical constituent studies have been conducted on these fruits. Hence in unripe fruits, a study on the constituents was performed and provided two new cucurbitane triterpene glycosides, 20-hydroxy-11-oxomogroside IA 1 (1) and 11-oxomogroside IIE (2), along with five known cucurbitane glycosides, 11-oxomogroside IA 1 (3), mogroside IIE (4), mogroside III (5), mogroside IVA (6), mogroside V (7), and two flavonoid glycosides, kaempferol 7-O-a-L-rhamnopyranoside (8) and kaempferol 3,7-di-O-a-L-rhamnopyranoside (9). Their structures were determined on the basis of detailed analyses of 1D, 2D-NMR spectroscopic methods and by comparing with literature values.4-11) Compounds 2 and 4 are the main constituents of unripe fruits and contribute to bitter taste. This paper deals with the first investigation of unripe bitter Lo Han Kuo fruits.Fresh unripe fruits were extracted with methanol. A suspension of methanol-extract in water was subjected to a high-porous polystynene gel, Diaion HP-20, which was successively eluted with H 2 O and 30%, 80%, and 100% methanol. The 80% methanolic eluate was chromatographed on silica gel, Sephadex LH-20 and reverse phase silica gel to afford nine glycosides, compounds 1-9, in yields of 0.0002%, 0.0068%, 0.00064%, 0.0081%, 0.0024%, 0.00019%, 0.0005%, 0.00081% and 0.0011%, respectively.Compound 1, a white amorphous powder, [a] D ϩ113.3°( MeOH), showed a quasi-molecular ion peak at m/z 654 [MϩH] ϩ and 654.4398 [MϩH] ϩ in the positive HR-FAB-MS, corresponding to the molecular formula C 36 ...

Three New Kaempferol Glycosides from Cardamine leucantha

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Cucurbitane Glycosides from Unripe Fruits of <i>Siraitia grosvenori</i>

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Herb-Derived Products: Natural Tools to Delay and Counteract Stem Cell Senescence

“…The fruits of Siraitia grosuenorii (Swingle) C. Jeffrey ex A.M. Lu & Zhi Y. Zhang, cultivated in China, are used as a natural sweetening agent and it has been reported to have beneficial effects in the diabetic subjects for its antihyperglycemic role [ 99 ]. Many reports have also shown that it has antitumoral and antioxidant properties [ 100 , 101 ].…”